Amplifier circuit utilizing characteristic correction and smooth curvilinear correction

Abstract

An amplifier circuit performs a characteristic correction process and a smooth curvilinear process on an input signal before being subjected to amplification. The characteristic correction process is a frequency characteristic process, which is performed on the input signal so as to produce a processed signal (Vp). Either the input signal or the processed signal, or the mixture of these signals is subjected to the smooth curvilinear process whose start point is designated by a state variation of amplification (VxTyp). Alternatively it is subjected to a gain decrement process instead of the smooth curvilinear process when the state variation of amplification is less than a default value (VxTHD). Thus, it is possible to prevent clipping from occurring in the amplified output signal while maintaining an adequate power.

1. An amplifier circuit comprising:
 a first gain correction unit converting an input signal into a first conversion signal; 
 a characteristic correction unit converting the first conversion signal into a second conversion signal in accordance with a characteristic correction process; 
 a smooth curvilinear correction unit converting the second conversion signal into a third conversion signal in accordance with a smooth curvilinear process in response to a state variable of amplification; 
 a second gain correction unit converting the third conversion signal into a fourth conversion signal; and 
 an amplification unit performing amplification on the fourth conversion signal, thus producing an output signal, 
 wherein the amplification unit generates the state variable of amplification so as to prevent clipping from occurring in the output signal. 
 
     
     
       2. The amplifier circuit according to  claim 1 , wherein the third conversion signal or the fourth conversion signal increases in level with less than an increment of the second conversion signal in accordance with the smooth curvilinear process. 
     
     
       3. The amplifier circuit according to  claim 1 , wherein the state variable of amplification represents a curvilinear start point from which the smooth curvilinear process is started on the second conversion signal. 
     
     
       4. The amplifier circuit according to  claim 1 , wherein when the second conversion signal has a maximum value, the smooth curvilinear process is performed such that a distortion factor of the output signal does not exceed a predetermined limit value. 
     
     
       5. The amplifier circuit according to  claim 1 , wherein when the state variable of amplification is less than a default value, the second conversion signal is subjected to a gain decrement process instead of the smooth curvilinear process. 
     
     
       6. The amplifier circuit according to  claim 5 , wherein the default value is determined in such a way that, when the second conversion signal has a maximum value, a distortion factor of the output signal, which is produced based on the second conversion signal subjected to the smooth curvilinear process whose start point is designated by the default value of the state variable of amplification, does not exceed a predetermined limit value. 
     
     
       7. The amplification circuit according to  claim 1 , wherein the characteristic correction process corresponds to a frequency characteristic process which is performed on the first conversion signal, and wherein the frequency characteristic process is changed with respect to a high-level portion and a low-level portion of the first conversion signal based on the default value of the state variable of amplification. 
     
     
       8. An amplifier circuit comprising:
 an amplifier that amplifies a first signal so as to produce a second signal; and 
 a corrector that receives a third signal so as to perform a smooth curvilinear process on a part or the entirety of the third signal based on a state variable, which varies in response to a state of the amplifier, thus producing the first signal, 
 wherein the smooth curvilinear process embraces a curvilinear process in which the third signal increases with a single unit of increment while the first signal increases with less than the single unit of increment, thus imparting a curvilinear characteristic to the third signal. 
 
     
     
       9. An amplifier circuit comprising:
 an amplifier that amplifies a first signal so as to produce a second signal; and 
 a corrector that receives a third signal so as to perform a smooth curvilinear process on a part or the entirety of the third signal based on a state variable, which varies in response to a state of the amplifier, thus producing the first signal, 
 wherein the corrector performs the smooth curvilinear process on a large-amplitude portion of the third signal, which is larger than the state variable, thus producing the first signal. 
 
     
     
       10. The amplifier circuit according to  claim 8 , wherein, with respect to the maximum value of the third signal, the smooth curvilinear process is performed on the third signal in such a way that a distortion factor of the second signal becomes lower than a predetermined value. 
     
     
       11. The amplifier circuit according to  claim 9 , wherein, with respect to the state variable less than a first constant which is determined in advance, the corrector does not perform the smooth curvilinear process but multiplies the third signal by a gain coefficient less than “1”, thus producing the first signal. 
     
     
       12. The amplifier circuit according to  claim 11 , wherein, with respect to the maximum value of the third signal, the first constant is determined such that a distortion factor of the second signal, which is produced by performing the smooth curvilinear process with a start point corresponding to the first constant on the third signal, becomes less than a predetermined value. 
     
     
       13. The amplifier circuit according to  claim 11  further comprising a characteristic corrector which receives a fourth signal and which chooses whether or not to perform a frequency characteristic process on a part or the entirety of the fourth signal based on the state variable, wherein the characteristic corrector changes the frequency characteristic process in response to a large-amplitude portion and a small-amplitude portion of the fourth signal compared to the first constant.